June 27, 2005

Big numbers and the meaning of life

Been away for a while. First breaking my ankle in a rock climbing accident. Basically a fight with cliff, I won. It ended up with bits missing and I didn't. They on a holiday that I had booked months ago and was going to take.

Anyhow this has left me with some thinking time. One of the things that I was thinking about was how life began, Creationists always say that there had to be a Creator because of the simple unlikelyhood as something as complex as a human spontaneously coming into being (forgetting of course that people didn't spontaneously come into being, they evolved). And they are right that to create chemicals capable of self replication is not trivial, however neither are the numbers involved. We are not talking about biology here, where numbers may be a few million to a few billion, but chemistry where you routinely deal with numbers so large that they have no names for them and that can only be expressed in terms of scientific notation.

Take a simple example, 1 litre of water. This small amount contains 3.3121 x 1025 molecules of water. If there is just one in a trillion (a level that is almost undetectable) replaced with an amino-acid, the building blocks from which all the known chemicals of life are made, it would still contain over 33 trillion. This is over 5 thousand (roughly 5059) for every man woman and child on the planet. Or over ten thousand ( roughly 10752) for every bas pair in the human genome. This is in one just litre of water and at an almost undetectably small concentration.

In the 1950's experiments where carried out as to if it where possible for amino-acids to form spontaneously in what they believed to be the conditions present in the earths very early history around 4 billion years ago (3999993994 years before many Creationists consider the universe to have come into being). The results where impressive, in only a few days the water in the experimental jar had turned green from the quantity and diversity of amino-acids produced. Today the consensus on the composition of the earths atmosphere in thoughts early days is different from in the 1950's but even with the less favorable conditions that are currently believed to have existed amino-acids are produced, and at levels that dwarf the parts per trillion used earlier.

Lets continue to use this level of one part per trillion, despite it being far far lower that any actual concentration in the early oceans.

The numbers in just 1 litre of water where vast, but what about when scaled up to the volume of the oceans? There are approximately 1.4 billion cubic kilometers of water in the worlds oceans. Each cubic kilometer contains 1 trillion litres, so the oceans contain 1.4 x 1021 litres of water. Using the number that I worked out earlier of 33 trillion amino-acids per litre (at a concentration of 1 amino-acid per trillion water molecules) that means that even at this miniscule concentration the worlds oceans would contain 4.62 x 1034 amino-acids, a truly mind boggling number.

With such enormous numbers involved it seems bazaar that not one would be configured so that it could take the other chemicals that it encountered around it and transform them into rough copies of itself. It would only take one, once that single lone individual happened to come into existence it would make more of itself, and the amount of this chemical precursor to life in the worlds oceans would grow exponentially turning it into a potent broth from which life to emerge. With numbers like 4.62 x 1034, or even larger, coupled with exponential growth suddenly life doesn't look as unlikely. In fact it looks very likely indeed.


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